1. Field of the Invention
The present invention relates to a device and process for sampling groundwater within a single monitoring well. More particularly, this invention relates to sampling of groundwater at several horizons independently within the monitoring well.
2. Description of Prior Art
It is often desirable to obtain samples of groundwater at various horizon locations within a well. In the past, multiple wells or complicated single well multiple sampling devices were required to accomplish multi-horizon sampling. These devices involve an elaborate system of sample lines and permanent packing or fragile small cross-section samplers placed on the well casing before its placement, requiring precise knowledge of horizon locations prior to casing installation. Sample cross-contamination between horizons can often occur with the use of existing devices. Furthermore, sample oxidation and/or degasification, which can ruin a sample value, are problems which may arise through the use of some existing devices for groundwater sampling.
An example of the prior art is U.S. Pat. No. 3,384,170 (Van Poollen) which discloses a sampler with a vertically stacked series of relatively small sampler chambers which fill simultaneously during sampling by means of apertures in each chamber and perforations in a cylindrical sleeve in communication with perforations in the well casing. The entire sampling unit, including the stacked series of sampler chambers, is then removed from the sleeve for testing. Van Poollen '170 relies primarily on vertical displacement of the sampler, relative to the cylindrical sleeve, to effect communication with the respective sampling horizon.